Electronic control system having predetermined output independent of input signal



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ETERMINED NPUT SIGNAL 1959 A. KUPFER ELECTRONIC CONTROL SYSTEM HAVING FRED OUTPUT INDEPENDENT OF I Filed Jan. 15

April 4, 1961 INVENTOR.

ARMIN KUPFER M W/W ATTORNEY 2,978,644 ICe Patented Apr. 4, 1961 ELECTRONIC CONTROL SYSTEM HAVING PRE- DETERMINED OUTPUT INDEPENDENT OF IN- PUT SIGNAL Armin Kupfer, 3190 20th St., Wyandotte, Mich.

Filed Jan. 15, 1959, Ser. No. 787,085

1 Claim. (Cl. 328-86) This invention relates to electronic control systems and more particularly to a system in which an input signal having predetermined characteristics will cause an output for a predetermined length of time which is independent of the duration of the input signal.

In certain control devices such as burglar alarms it is desirable to have an output signal which is initiated by a particular input signal but which lasts for a period of time which is independent of the duration of the input signal. Thus, in an alarm which senses the presence of an intruder in the area of a building the control system should provide an alarm signal which is initiated when the intruder first comes within range of the alarm, but which continues to operate for a predetermined length of time even if the intruder leaves the vicinity of of the alarm. The control device necessarily initiates its output only upon receiving signals of a particular magnitude and configuration.

The present invention contemplates a control device of this nature which is extremely simple in construction and provides trouble free operation with a minimum of maintenance.

It is also desirable that the control be operative with a wide variety of input devices and provide an output signal which may easily be adapted to a wide variety of controlled devices such as bell or siren alarms or floodlight systems.

Another object is to provide a control system which may be used in alarm devices which have a low electrical power consumption when in a standby state so that it may be continuously operative without incuring large electrical costs.

One embodiment'of the invention which meets the above requirements has as its input a transducer which converts a physical condition to an electrical impulse. Such a transducer may be a microphone. An input signal is applied to three stages of capacitor coupled voltage amplification.

The third stage is capacitor coupled to a power amplifier which has a relay in its plate circuit. The cathode of the third stage is connected to ground through a pair of normally closed contacts on this plate relay. When the transducer emits a signal of particular magnitude and configuration, the plate relay is energized, disconnecting the cathode of the third stage from the ground. This produces a relatively high voltage at the plate of the third stage which maintains the relay in an actuated condition until the charge on the coupling capacitor between the third and power stages is discharged to ground through a grid resistor. By varying the size of this grid resistor the period of time during which the relay is actuated may be controlled.

Other objects, advantages and applications of the present invention will be apparent by the following detailed description of this preferred embodiment of the invention. The description makes reference to the accompanying drawing which is a schematic representation of the circuitry of the preferred embodiment.

The device is powered by line voltage which is applied to the primary coil of a power transformer 10. The transformer 10 has two secondary windings, one of which, 12, connects to the filiments of all the amplifier stages. The other winding 14 provides a high voltage which is applied between ground and the plate of a rectifier tube 14 The filament of the rectifier 14 is connected across the line through a voltage reducing resistor 16. The cathode of the rectifier 14 is connected to one end of a filter comprising two electrolytic capacitors 18 and a resistance 20. This filter acts to smooth out the rectified half cycle current received from the tube 14.

A sensing device 22 is preferably a crystal microphone which will provide electrical output pulses which are a function of a sound input. Other transducer devices such as photo cells, proximity pickups and the like could also be utilized with this preferred embodiment. The sensing device 22 provides an output across a matching resistance 24, one end of which is grounded. The other end connects to the grid of a first amplifier tube 26. The cathode of the tube 26 is grounded in the normal manner and its plate is connected to the direct current supply through a resistance 28.

A capacitor 30 and a grounded resistance 32 capacitor couple the tube 26 to a second amplifier tube 34. The cathode of the tube 34 is grounded, the plate is connected to a pulsating direct current supply through a resistance 36, and the stage is coupled to a following amplifier tube 38 by means of a capacitor 40 and a grounded resistance 42.

The sizes of the resistances 24, 32, and 42 and the capacitors and 40 may be adjusted, as may the parameters skilled in the art.

The cathode of the amplifier 38 is normally connected to ground through a resistance 44 and the normally closed contacts 46 of a relay generally inicated at 48. The anode of the tube 38 is connected to the voltage supplythrough a resistance 50 and is connected to the grid of" the succeeding amplifier stage 52 through a capacitor 54.. The grid is grounded through a variable resistance 56. The cathode of the stage 52 is also grounded through another variable resistor 58. The relay 48 is connected in the plate circuit of the tube 52 between the plate and the voltage supply. It is shunted by a capacitor 60 which acts to reduce the chatter of relay contacts. The relay, in addition to its normally closed contact 46, has a normally open contact 62 which provides the controlled output voltage.

When the sensing device 22 provides a signal of the proper magnitude and frequency it is amplified by the tubes 26, 34, 38 and 52 and their associated circuitry, and thereby energizes the relay 48. This causes the normally closed contacts of the relay 48 to open and closes the normally open contacts 62. The closing of the contacts 62 will connect the controlled device to the line voltage.

The opening of the normally closed contacts 46 disconnects the cathode resistor 44 of the tube 38 from ground. This greatly increases the voltage which appears across the tube 38 and will cause this voltage to appear across the capacitor 54. In this matter the tube 52 will continue to receive a signal which will maintain the relay 48 in an energized condition independently of the furtherdependent on the ratio between the capacitor 54 and the resistance 56. When the voltage across the capacitor 54 has diminished beyond a certain point the current of? 3 the tube 52 will no longer receive sufficient voltage to maintain the coil of the relay 48 energized. If, at this time, the sensing device 22; is providing a proper signal the relay 48 will he maintained in a closed condition.

The variable resistor 58 in the cathode circuit of the tube 52 may be used to adjust the initial voltage at which the relay 46 is energized.

It is to be understood that the present invention is not limited to use with controlled devices which use line current. Any other current source might be utilized in connection with the normally open contacts 62 of the relay 48. Similarly any of a wide variety of transducer devices might replace the microphone sending device 22.

Having best described my invention 1 claim:

An electronic alarm system operative to provide an output signal for a fixed period of time upon the receipt of an input signal above a threshold level from a transducer, comprising: a first vacuum tube amplifier; a second vacuum tube amplifier; a capacitor connecting the plate of said first vacuum tube amplifier to the grid of said second vacuum tube amplifier; a variable resistanceconnecting the grid of said second vacuum tube amplifier to ground; a relay in the plate circuit of said second vacuum tube amplifier, said relay having a pair of normally closed contacts, one of which connects to the cathode of said first vacuum tube amplifier and the other which connects to ground potential of the system, whereby upon receipt of a signal of a threshold level at the grid of said second vacuum tube amplifier said plate relay is energized opening the normally closed contacts, ungrounding the cathode of said first vacuum tube amplifier, and placing a potential upon said capacitor which is sufi'icient to maintain said relay in a closed position independent of the further signal level received by the system until such time as a particular proportion of the charge upon said capacitor is dissipated to ground through said variable resistance such time depending upon the setting of said resistance.

References Cited in the file of this patent UNITED STATES PATENTS 20 2,678,411 Hufnagel May 11, 1954 2,777,097 Atkins '-a Ian. 8, 1957 2,830,192 Atkins Apr. 8, 1958 

